a) Field of the Invention
The invention relates to a means for checking the lamp of a light source unit producing the illuminating light for an endoscope and a light-guide cable which conveys the illuminating light to the object being observed
b) Description of the Prior Art
To examine cavities which are difficult of access, such as body cavities, use is made of endoscopes. Since the objects which are of interest in the cavities are often photographed or shown in monitors by means of television cameras, the endoscopes employed use controllable illumination facilities which are intended to ensure that the objects being observed are ideally illuminated. In this case the light produced by the light sources is transmitted to the endoscope along light-guide cables.
The operation of the light-guide cable of endoscopic apparatus may be adversely affected by the fracture of individual fibers, e.g. due to severe bending stresses, by ageing or by similar causes, and this may mean that the objects to be viewed with the endoscope can no longer be properly illuminated. Particularly with arc lamps, there is also a reduction in the quantity of light which can be emitted as the time in use lengthens, so that illumination is degraded for this reason too. Hence it is useful in endoscopic applications, and particularly in medicine, for it to be possible for the correct operation of the means of illumination to be checked. What is achieved by making a check of this kind is that faulty operation of the means of illumination or the light-guide cable is detected before the endoscope is introduced into the body cavity and in this way any unnecessary stress on the patient caused by the replacement of a faulty light-guide cable or a lamp which is no longer producing enough light can be avoided.
A method of checking a light source for endoscopes is known from DE-OS 3515612. In the embodiment disclosed therein what are checked are the light emitted from the lamp when operating continuously and as a flash-lamp, the operation of the shutter vane, the operation of the diaphragm and the data transmission between control unit and camera. What is not checked is the operation of the light-guide cable.
Another means of checking the supply of light can be seen in the operating instructions for a light source with a diaphragm controlling arrangement which is made by the Dyonics Company. It includes an arrangement for checking the light-guide cable. To check the lamp, its brightness is sensed by a photo-resistor and is shown in the form of a bar plot. To check the light-guide cable, it is inserted in the socket of a brightness measuring device, which causes the controller of the motor driving the diaphragm to open the latter completely. The brightness level so measured is also shown as a bar plot, and the height of the bar provides information on the condition of the lamp and light guide cable.
One disadvantage from which this means suffers is that the system has to be calibrated to suit the diameter of the bundle of fibers making up the light-guide cable which is used and if a fiber bundle of a different diameter is used, there are inaccuracies in the measurements. Also, the brightness levels measured are merely indicated and the user has to interpret these levels for himself, i.e. has to estimate the transmission for himself, and because of this misinterpretations cannot be ruled out.
Hence the main object of the present invention is to provide a means of measurement for light sources for endoscopes with which the lamp and the light-guide cable can be checked for satisfactory operation by automatic analysis.